1. Field of the Invention
The present invention relates to an imaging apparatus provided with an image pickup device such as a CCD, and a drive control method for an image pickup device.
2. Description of the Related Art
Conventionally, a CCD (charge-coupled device) has widely been used as an image pickup device in imaging apparatuses such as digital still cameras. The CCD has light receiving elements such as photodiodes, each light receiving element stores a charge corresponding to an amount of received light, and the stored charges are read out through vertical transfer paths and a horizontal transfer path.
In the above-described type CCD, horizontal pixel addition has been achieved, for example, by temporarily stopping horizontal transfer to add adjacent pixels (see, for example, Japanese Unexamined Patent Publication No. 6 (1994)-078101), by providing a transfer path serving as a buffer between the vertical transfer paths and the horizontal transfer path (see, for example, U.S. Pat. No. 7,002,630), or by providing a line memory and gradually driving the horizontal transfer path during blanking periods of vertical transfer (see, for example, U.S. Patent Application Publication No. 20030169355 and Japanese Unexamined Patent Publication No. 2002-112119).
However, there is a problem in the conventional horizontal pixel addition schemes that only horizontally adjacent pixels can be added, and if the horizontally adjacent pixels have different colors, the colors are mixed. On the other hand, in CCDs that are designed to prevent mixing of colors, the number of added pixels in the horizontal direction and a positional relationship between added pixels are fixed, and there is little flexibility in outputted images. Further, such CCDs necessitate a complicated driving method to achieve the horizontal addition.